Prosthetic tooth simulating a natural tooth having a filling and method of making the same



May 21, 1957 w. NEUMAYER 2,792,628 PROSTHETIC TOOTH SIMULATING A NATURALTOOTH HAVING A FILLING AND METHOD OF MAKING THE SAME Jan. 25, 1955 Filed1 mmvrozc WIH'IQIM Neum MueJM Unite Sttes Patent PROSTHETIC TOOTHSIIVIULATING A NATURAL TOOTH HAVING A FILLING AND METHOD OF MAKING THESAME Wilhelm Neumayer, Heilbronn, Germany Application January 25, 1955,Serial No. 483,937 Claims priority, application Germany January 29, 19548 Claims. (Cl. 32-8) The present invention relates to a prosthetic toothsimulating a natural tooth having a filling, and to a method of makingthe same. More particularly, the present invention relates to aprosthetic tooth appearing to have a filling, such as gold or amalgamfillings which are customarily applied to a natural tooth, so as to moreclosely simulate a natural tooth.

It is known to put fillings into prosthetic teeth which do not onlysimulate the fillings made in natural teeth but which are actually madeby the same method which is used for the filling of natural teeth.According to the customary procedure, a hole is bored into theprosthetic tooth at the desired spot which will be potentially visiblewhen the prosthetic tooth is placed in a persons mouth, and the hole isfilled just like cavities in natural teeth are filled. It is adisadvantage of this process that relatively large quantities of fillingmaterial have to be used, thus increasing the cost when precious metalsor their alloys are applied. Furthermore, the filling of the prosthetictooth made by these customary methods comes in contact with the contentsof the oral cavity and thereby is exposed to attack by chemically activesubstances.

It is an object of the present invention to overcome the aforementioneddisadvantages.

It is a further object of the present invention to provide a prosthetictooth closely simulating a natural tooth having a filing, thereby usingconsiderably smaller quantities of filling material than were heretoforeneeded for this purpose.

It is still another object of the present invention to join the fillingsimulating material to the prosthetic tooth so as to prevent itsexposure to the oral cavity and thereby avoiding chemical reactionswhich might damage the material. 7

With the above objects in view, the present invention mainly consists ina false tooth comprising, in combination, a prosthetic tooth ofartificial tooth-simulating material, a thin metal body joined to theprosthetic tooth on a portion of the tooth visible when the prosthetictooth is in a persons mouth so that the false tooth in a persons mouthappears to have a filling and thereby more closely simulates a naturaltooth having a filling, and a layer of transparent plastic covering atleast the metal body portion of the false tooth and protecting the metalbody.

The present invention also comprises in a method of making a falsetooth, the steps of joining to the surface of a prosthetic tooth ofartificial tooth-simulating material a thin metal body, and covering thesurface of at least the thin metal body with a thin layer ofsolidifiable transparent plastic material.

In accordance with the present invention, a thin metal body is joined toa prosthetic tooth made of porcelain or plastic synthetic material andcovered with a transparent layer of synthetic plastic material. Theporcelain or the synthetic plastic material of which the prosthetictooth is formed may contain coloring materials so as to closely resemblethe color of a natural tooth. The surface of the thin metal body inaccordance with the present invention simulates the surface appearanceof a Patented May 21, 1957 filling in a natural tooth both as to colorand shape. The synthetic plastic layer covering the surface of the metalbody may also cover adjoining surface portions or the entire surface ofthe prosthetic tooth. This covering layer is preferably made ofcolorless, transparent material so as not to be visible when the falsetooth is in a persons mouth.

Various methods for the making of a false tooth can be used inaccordance with the present invention, depending on whether the metalbody is to be joined to a finished prosthetic tooth of either porcelainor synthetic plastic material, or whether the metal body is to 'bejoined to a prosthetic tooth of synthetic plastic material during themaking of the same.

According to a method of the present invention a false tooth may bemolded by first covering at least a portion of the inner surface of atooth-forming mold with a synthetic material adapted to form uponheating a hard transparent layer, placing a thin metal body in the moldon the portion thereof which iscovered by the synthetic material,filling the mold with artificial tooth-simulating material which isadapted to harden upon heating under pressure, heating the mold withthese materials and the metal body therein under pressure so as to forma hard body having the shape and appearance of a tooth, and removing thethus formed false tooth from the mold, the false tooth simulating anatural tooth having a filling.

In order to join a thin metal body to a previously formed prosthetictooth in accordance with the present invention so as to simulate atooth-filling, a shallow indentation of desired dimensions is formed inthe surface of a plastic tooth, preferably by abrasive methods, and athin metal body of such dimensions as to substantially fill theindentation is placed therein.

When it is desired to join a thin metal body to a prosthetic tooth madeof porcelain, the method of the present invention also includes the stepof forming a shallow indentation in the surface of the porcelain tooth.In a preferred execution of the method of the present invention thesurface of the indentation in a porcelain tooth is roughened andthereafter moistened with a syrupy synthetic plastic material,preferably belonging to the group of ethylene oxides or polyurethanes.The thin metal body is then fitted into the indentation and adhered tothe surface thereof by the adhesive qualities of the synthetic syrupymaterial. Again, the dimensions 'of themetal body approximate thedimensions of the indentation. At least the surface of the metal bodyand, if desired, also adjoining portions of the surface of the porcelaintooth are then covered with a thin layer 'of transparent plasticsynthetic material. Preferably ethylene oxides or polyurethanes are usedfor this purpose. The synthetic plastic layer adhering the thin metalbody to the surface of the indentation and the synthetic plastic layercovering the free surface of the metal body are then polymerized, forinstance by heating the false tooth for about 15 minutes to atemperature of about 200 C. It is most preferred to use a plasticsynthetic material in connection with a porcelain tooth a syntheticresin belonging to the group of ethylene oxide resins since these resinspossess a glass-like transparency, have affinity to porcelain andpolymerize without contraction in volume. These resins penetrate themicroscopic and capillary apertures in the surface of the porcelaintooth and thereby form an extremely intimate connection. Furthermore,the resins to which the present invention is applicable are insoluble,non-poisonous and possess great strength, all of which qualities arevery desirable in a transparent layer according to the presentinvention.

In accordance with another preferred embodiment of the present inventionthe false tooth having the layer of transparent material thereon ispolished at least on that portion of its surface which is covered by thetransparent plastic material. It is therefore advisable to provide for asmall surplus thickness ofthe plastic layer which will be removed duringthepolishing process.

It will be apparent from the forgoing that a large percentage of theprecious metal or precious metal alloy customarily used for fillings offalse teeth is saved by replacing the conventionalfilling with the thinmetal body of the present invention. It will also beapparent that thesimulated filling provided by the present invention is not exposed tochemical or mechanical injury because it is protected by the transparentsynthetic layer.

The synthetic plastic tooth-simulating material from ch. h Pr he c tootho he p e n n t on s formed canbe any synthetic plastie materialcustomarily ssdi r he. m nufac ure o pro t e i s o quently it iscomposed of polyacrylj and polymethacryl acid methyl esters. Theprosthetic tooth may also be formed from the monomer compoundina dryprocess by heating to about 170C. under high pressures, or it may beformed from powder and liquid by heating to about 100 C; Acrylates whichare commercially available for the purpose of forming prosthetic teethare sold under a variety of trademarks such as for instance Paladon,Palapont, or Lucite. Customarily they are colored so as tomore closelysimulate the color of natural teeth.

Porcelain teeth consist of porcelain compositions well known in the artand contain as coloring agents preferably metal oxides so as to closelysimulate the color of natural teeth.

The transparent layer with which the metal body joined to a syntheticplastic tooth is covered, consists preferably ofsynthetic plasticmaterial belonging to the groups of polyacryl and polymethacryl acidmethyl esters, such as are also used for forming the synthetic plastictooth. However, other synthetic plastics having similar physical andchemical characteristics may also be used.

The synthetic plastic materialsused' for adhering the metal body to aporcelain tooth and for covering the metal body joined to a porcelaintooth preferably belong to the groups of ethylene oxides orpolyurethanes.

The thin metal bodies are preferably made of precious metals or alloysof the same and most preferably of gold 'or gold alloys.

The thickness of the thin metal bodies is preferably kept to between 0.1mm. and 0.02 mm. and most preferably to approximately 0.05 mm.

The thickness of the transparent layer which covers atleast the freesurface of the metal body in accordance with the present inventionispreferably kept at between 0.3 and 0.1 mm. and most preferably atapproximately 0.2mm.

The previously mentioned ethylene oxides andtransparent, polyurethanesare only used in connection with porcelain teeth and not in connectionwith teeth made of synthetic plastic materials since tempertures of atleast between 150 C. and 160 C. are required for their polymerization. Aprosthetic tooth made of porcelain can easily'withstand thesetemperatures while prosthetic teeth made of synthetic plastic materialsincur structural damage when exposed to such high temperatures withoutcon; current considerable increase in pressure. To the extent to whichit becomes possible to polymerize and harden the polyurethane resins andethylene oxides at lower temperatures, it will also be possible to usethese resins as transparent layer on synthetic plastic teeth.

The following examples are given to further. illustrate the process ofthe present invention, the scope of the invention not however beinglimited to the specific details of the examples.

EXAMPLE 1 Making of a prosthetic tooth with a simulated filling frommonomeric acrylate A thin layer of colorless acrylatepowder such asLucite a tooth mold, corresponding to the surface portion of theprosthetic tooth on which the simulated filling is to be located. Thiscorresponds to the layer covering metal body 3 of Pig. 1 of the drawing,as will be more clear from the specific description, ofthe drawing.

A small circular gold plate having a thickness of 0.05 mm., and adiameter of 2 mm. is positioned on the acrylate powder.

Thereafter the mold is filled with acrylate powder suitably colored soas to simulate the color of natural tooth.

The mold is closed and heated for about 10 minutes to about 170 C. at apressure of 10 atmospheres.

The mold remains in the press until it is cooled, thereafter it isopened, the prosthetic tooth is taken from the mold, the mold-flashremoved, and the thus formed false tooth is polished.

EXAMPLE 2 Making of a prosthetic tooth with a simulated filling frompolymeric acrylate A thin layer of-colorless polymeric acrylate suchasfon instance Palapont of dough-like consistency isplaced on a portionof the inner surface of a tooth mold.

A small rectangular goldalloy. plate having a gold content of athicknessof 0.07 mm., a length of 2 /2 mm. and a width of 1 /2 mm. is positionedon the doughlike polymeric acrylate mass.

Thereafter the mold is filled with polymeric acrylate of dough-likeconsistency which has been suitably colored so as to simulate the-colorof a natural tooth.

The surplus is squeezed out of the mold, the mold is closed and heatedfor 1 hour to C. under an excess pressure of betweenS and 5 atmospheres.

After cooling of the mold, the tooth is finished as-described in Example1.

EXAMPLE 3 Making of a simulated filling on a prosthetic tooth consisling of synthetic plastic material EXAMPLE 4 Making of'a;,simulatedfilling on,a pr0sthetic tooth c0nsisting of. porcelain Ashallowindentation is ground in the chosen portion of the surface of theprosthetictooth. This indentation is 0.05 mm deep, of approximatelycircular shape, having a diameter of 2 /2 mm.

The surface of the indentation is moistened with a colorless,transparent polyurethane resin.

A gold alloy plate containing 90% of gold and dimensioned so as'to fitinto the indentation is placed therein.

The free surface of the plate and the surroundingsurface-area-of theporcelain tooth are covered with a polyurethane layer having athickness'of 0.15 mm.

The polyurethane is polymerized by heating of the prosthetic tooth on ahot plate to 200 C. keeping it at that temperature for 15 minutes.

After grinding 01% any excess of the transparent plastic material, theplastic covered area of the prosthetic tooth is polished.

The novel features-which are considered as characteristic fortheinvention are set forth in particularin the appended claims. Theinvention itself, however, both' as to itsconstruction and its method ofoperation, togethenwith additional objects and advantages thereof, willbe bestunderstoodfrom thefollowingdescription of spe-- cific embodimentswhen read in connection with the accompanying drawings, in which:

Fig. 1 is a cross section through tooth-forming mold and a prosthetictooth according to the present invention; and

Fig. 2 is a perspective view of a false tooth according to the presentinvention.

Referring now to the figures, and more particularly to Fig. 1, aprosthetic tooth of synthetic plastic material is made in accordancewith the present inv n ion by placing a thin layer 2 of colorlesstransparent p re material into the lower half 1 of the mold, thereafterplacing a thin metal body 3 on a portion of the lower par-t l of themold corresponding to the surface portion of the prosthetic tooth onwhich the simulated filling is to In the illustrated embodiment thecolorless plastic layer 2 has also been applied to the inner surfs e ofthe upper portion 5 of the mold. lower part 1 of Thereafter the the moldand the upper part 5 of the mold are completely filled with a coloredplastic 4. The two parts of the mold are put together and the falsetooth is formed by application of heat and pressure as previouslydescribed.

The false tooth shown in Fi ure 2 comprises a prosthetic tooth 7 made ofporcelain, a thin metal body 8 simulating a filling, and a thincolorless transparent layer 9 covering the metal body. This plasticlayer 9, due to its being transparent and colorless, while indicated inthe drawing cannot actually be seen when the false tooth is in a personsmouth.

It will be understood that each of the elements described above, or twoor more together, may also find a useful application in other types offalse teeth differing from the types described above.

While the invention has been illustrated and described as embodied inprosthetic teeth, it is not intended to be limited to the details shown,since various modifications and structural changes may be made withoutdeparting in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can by applying current knowledgereadily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this inventionand, therefore, such adaptations should and are intended to becomprehended within the meaning and range of equivalence of thefollowing claims.

What is claimed as new and desired to be secured by Letters Patent is:

l. A false tooth comprising, in combination, a prosthetic tooth ofporcelain tooth-simulating material; a thin metal body joined to saidprosthetic tooth on a portion of said tooth visible when said prosthetictooth is in a persons mouth so that said false tooth in a persons mouthappears to have a filling and thereby more closely simulates a naturaltooth having a filling; and a transparent layer made of transparentsynthetic plastic material selected from the group consisting oftransparent water insoluble polymerized ethylene oxides and transparentpolyurethanes covering at least said metal body portion of said falsetooth and protecting said metal body.

2. A false tooth comprising, in combination, a prosthetic tooth ofporcelain tooth-simulating material; a thin metal body joined to saidprosthetic tooth on a portion of said tooth visible when said prosthetictooth is in a persons mouth so that said false tooth in a person's mouthappears to have a filling and thereby more closely simulates a naturaltooth having a filling; a layer of synthetic plastic material selectedfrom the group consisting of water insoluble polymerized ethylene oxidesand polyurethanes adhering said thin metal body to said portion of saidtooth; and a transparent layer made of transparent synthetic plasticmaterial selected from the group consisting of transparent waterinsoluble polymerized ethylene oxides and transparent polyurethanescovering at least said metal body portion of said false tooth andprotecting said metal body.

3. In a method of making a false tooth, the steps of forming a shallowindentation in a portion of the surface of a prosthetic tooth saidportion being visible when said prosthetic tooth is in a persons mouth;placing into said indentation a thin metal body being so dimensioned asto substantially fill said indentation; and covering the surface of atleast said thin metal body with a thin layer of solidifiable transparentplastic material.

4. In a method of making a false tooth, the steps of forming a shallowindentation in a portion of the surface of a prosthetic tooth saidportion being visible when said prosthetic tooth is in a persons mouth;covering the surface of said indentation with an adhesive latentlyhardenable synthetic material; placing into said indentation andadhering to the surface thereof by means of said ad- 'hesive material athin metal body being so dimensioned as to substantially fill saidindentation; and covering the surface of at least said thin metal bodywith a thin layer of solidifiab'le transparent plastic material.

5. In a method of making a false tooth, the steps of forming a shallowindentation in a portion of the surface of a prosthetic tooth saidportion being visible when said prosthetic tooth is in a persons mouth;roughening the surface of said indentation; covering the surface of saidindentation with an adhesive latently hardenable synthetic material;placing into said indentation and adhering to the surface thereof bymeans of said adhesive material a thin metal body being so dimensionedas to substantially fill said indentation; and covering the surface ofat least said thin metal body with a thin layer of solidifiable transparent plastic material.

6. In a method of making a false tooth, the steps of joining to thesurface of a prosthetic tooth of artificial tooth-simulating material athin metal body; covering the surface of at least said thin metal bodywith a thin layer of solidifiable transparent plastic material; andpolishing at least the portion of the surface of said false tooth havingsaid layer of transparent plastic material thereon.

7. A false tooth comprising, in combination, a prosthetic tooth ofporcelain tooth-simulating material; a thin metal body joined to saidprosthetic tooth on a portion of said tooth visible when said prosthetictooth is in a persons mouth so that said false tooth in a persons mouthappears to have a filling and thereby more closely simulates a naturaltooth having a filling; and a transparent layer made of transparentpolyurethane covering at least said metal body portion of said falsetooth and protecting said metal body.

8. A false tooth comprising, in combination, a prosthetic tooth ofporcelain tooth-simulating material; a thin metal body joined to saidprosthetic tooth on a portion of said tooth visible when said prosthetictooth is in a persons mouth so that said false tooth in a persons mouthappears to have a filling and thereby more closely simulates a naturaltooth having a filling; a layer of polyurethane adhering said thin metalbody to said portion of said tooth; and a transparent layer made oftransparent polyurethane covering at least said metal body portion ofsaid false tooth and protecting said metal body.

References Cited in the file of this patent UNITED STATES PATENTS325,626 Phillips Sept. 1, 1885 2,302,375 Myerson Nov. 17, 1942 2,393,817Schlosser et a1. Jan. 29, 1946 2,677,150 Rydin May 4, 1954

1. A FALSE TOOTH COMPRISING, IN COMBINATION, A PROSTHETIC TOOTH OFPORCELAIN TOOTH-SIMULATING MATERIAL; A THIN METAL BODY JOINED TO SAIDPROSTHETIC TOOTH ON A PORTION OF SAID TOOTH VISIBLE WHEN SAID PROSTHETICTOOTH IS IN A PERSON''S MOUTH SO THAT SAID FALSE TOOTH IN A PERSON''SMOUTH APPEARS TO HAVE A FILLING AND THEREBY MORE CLOSELY SIMULATES ANATURAL TOOTH HAVING A FILLING; AND A TRANSPARENT LAYER MADE OFTRANSPARENT SYNTHETIC PLASTIC MATERIAL SELECTED FROM THE GROUPCONSISTING OF TRANSPARENT WATER INSOLUBLE POLYMERIZED ETHYLENE OXIDESAND TRANSPARENT POLYURETHANES COVERING AT LEAST SAID METAL BODY PORTIONOF SAID FALSE TOOTH AND PROTECTING SAID METAL BODY.